<!DOCTYPE html>
<html>
    <head>
        <script>
        var txt="";
        function message(){
            try {
                adddlert("wellowcome guest!");
            }
            catch(err ){
                txt="本页有一个错误。\n\n";
                txt+="错误描述：" + err.message + "\n\n";
                txt+="点击确定继续。\n\n";
                alert(txt);
            }
        }
        </script>


    </head>
    <body>
        <input type="button" value="查看消息" onclick="message()"/>
        
    </body>
</html>